East Berlin had trams, West Berlin had double decker buses. The doubledeckers can’t pass safely below the wires of the tram, so if you see a tram you are in former east Berlin, but if you see a doubledecker you are in former west. At least that’s what my friend told me years ago who lived in Berlin for some years. Can someone confirm this? I can’t find any info on this on the internet.
As an east Berliner we have trams and no double deckers, but I have only seen double deckers near the center of the city.
I can’t remember seeing them in the places with trams, but I don’t see them much at all. This is my limited observation, as I don’t use busses as much as trains and don’t know the west as well as the east.
If you really care I can cycle out (in?) on the weekend and check.
Edit: added my bias